Signal processing method for low-cost device, and apparatus for same

ABSTRACT

The present invention relates to a wireless communication system. The present invention relates more particularly to a method and an apparatus for receiving a downlink signal by a device in a wireless communication system, the method comprising the steps of: receiving from a subframe a first PDCCH comprising scheduling information about first common data; receiving from the subframe a second PDCCH comprising scheduling information about second common data; and, on the basis of Ta, a TB size of the first common data and Tb, a TB size of the second common data, controlling a procedure for receiving downlink data from the subframe, wherein if T1&lt;Ta&lt;=T2 and T1&lt;Tb&lt;=T2, performed is a procedure for processing reception signal with respect to the first common data or the second common data.

TECHNICAL FIELD

The present invention relates to a method of receiving/processing asignal in a wireless communication system and apparatus for the same.More particularly, the present invention relates to a method ofreceiving/processing a signal for a low-price user equipment andapparatus for the same.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice or data. Ingeneral, a wireless communication system is a multiple access systemthat supports communication of multiple users by sharing availablesystem resources (a bandwidth, transmission power, etc.) among them. Forexample, multiple access systems include a Code Division Multiple Access(CDMA) system, a Frequency Division Multiple Access (FDMA) system, aTime Division Multiple Access (TDMA) system, an Orthogonal FrequencyDivision Multiple Access (OFDMA) system, a Single Carrier FrequencyDivision Multiple Access (SC-FDMA) system, and a Multi Carrier FrequencyDivision Multiple Access (MC-FDMA) system. In a wireless communicationsystem, a User Equipment (UE) may receive information from a BaseStation (BS) on a Downlink (DL) and transmit information to the BS on anUplink (UL). The UE transmits or receives data and various types ofcontrol information. Various physical channels exist according to thetypes and usages of information that the UE transmits or receives.

DISCLOSURE OF THE INVENTION Technical Task

The technical task of the present invention is to provide an efficientmethod of receiving/processing a signal in a wireless communicationsystem and apparatus for the same. Particularly, the technical task ofthe present invention is to provide a method of receiving/processing asignal for a low-price user equipment and apparatus for the same.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solutions

In one technical aspect of the present invention, provided herein is amethod of receiving a downlink signal by a user equipment in a wirelesscommunication system, including receiving a first PDCCH (PhysicalDownlink Control Channel) including a scheduling information on a firstcommon data in a subframe, receiving a second PDCCH including ascheduling information on a second common data in the subframe andcontrolling a process for receiving a downlink data in the subframebased on TB (Transport Block) size Ta of the first common data and TBsize Tb of the second common data, wherein if T1<Ta≦T2 and T1<Tb≦T2, areceived signal processing is performed on the first common data or thesecond common data, wherein if Ta≦T1 and T1<Tb≦T2 or T1<Ta≦T2 and Tb≦T1,the received signal processing is performed on both the first commondata and the second common data, wherein the T1 indicates a maximum TBsize in case of receiving a unicast data solely, and wherein the T2indicates a maximum TB size in case of receiving a common data solely.

In another technical aspect of the present invention, provided herein auser equipment used for a wireless communication system, including an RF(Radio Frequency) unit and a processor, wherein the processor isconfigured to receive a first PDCCH (Physical Downlink Control Channel)including a scheduling information on a first common data in a subframe,receive a second PDCCH including a scheduling information on a secondcommon data in the subframe and control a process for receiving adownlink data in the subframe based on TB (Transport Block) size Ta ofthe first common data and TB size Tb of the second common data, whereinif T1<Ta≦T2 and T1<Tb≦T2, a received signal processing is performed onthe first common data or the second common data, wherein if Ta≦T1 andT1<Tb≦T2 or T1<Ta≦T2 and Tb≦T1, the received signal processing isperformed on both the first common data and the second common data,wherein the T1 indicates a maximum TB size in case of receiving aunicast data solely and wherein the T2 indicates a maximum TB size incase of receiving a common data solely.

The first common data may include an SIB (System Information Block) andthe second common data may include an RAR (Random Access Response)

If T1<Ta≦T2 and T1<Tb≦T2, the received signal processing may beperformed on only the SIB among the SIB and the RAR.

If T1<Ta≦T2 and T1<Tb≦T2, the received signal processing may beperformed on only the RAR among the SIB and the RAR.

If T1<Ta≦T2 and T1<Tb≦T2 and if the RAR is transmitted as a part of acontention-based RACH (Random Access Channel), the received signalprocessing may be performed on only the SIB among the SIB and the RAR.

If T1<Ta≦T2 and T1<Tb≦T2 and if the RAR is transmitted as a part of anon-contention-based RACH process, the received signal processing may beperformed on only the RAR among the SIB and the RAR.

Advantageous Effects

According to embodiments of the present invention, a signal can beefficiently received/processed in a wireless communication system.Particularly, a signal can be efficiently received/processed in alow-price user equipment.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 illustrates physical channels and a general signal transmissionmethod using the physical channels in a Long Term Evolution(-Advanced)(LTE-(A)) system.

FIG. 2 illustrates a radio frame structure in the LTE(-A) system.

FIG. 3 illustrates a resource grid of a slot.

FIG. 4 illustrates an exemplary Downlink (DL) SubFrame (SF) structure.

FIG. 5 illustrates an example of allocating Enhanced Physical DownlinkControl Channels (E-PDCCHs) to an SF.

FIG. 6 illustrates an Uplink (UL) SF structure.

FIG. 7 illustrates a random access procedure.

FIG. 8 illustrates an example of a process for receiving a downlinksignal according to one embodiment of the present invention.

FIG. 9 illustrates block diagrams of a base station and a user equipmentapplicable to an embodiment of the present invention.

BEST MODE FOR INVENTION

The configuration, operation, and other features of the presentinvention will readily be understood with embodiments of the presentinvention described with reference to the attached drawings. Embodimentsof the present invention may be used for various radio access systemssuch as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier FrequencyDivision Multiple Access (SC-FDMA), Multi-Carrier Frequency DivisionMultiple Access (MC-FDMA), etc. CDMA may be implemented as a radiotechnology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications/General packet Radio Service/EnhancedData Rates for GSM Evolution (GSM/GPRS/EDGE). OFDMA may be implementedas a radio technology such as Institute of Electrical and ElectronicEngineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Evolved UTRA (E-UTRA), etc. UTRA is a part of Universal MobileTelecommunications System (UMTS). 3rd Generation Partnership ProjectLong Term Evolution (3GPP LTE) is a part of Evolved UMTS (E-UMTS) usingE-UTRA, and LTE-Advanced (LTE-A) is an evolution of 3GPP LTE.

While the embodiments of the present invention will be described belowmainly in the context of a 3GPP system, this is purely exemplary andthus should not be construed as limiting the present invention.

While the present invention is described in the context of an LTE-Asystem, the proposed concept or methods of the present invention andembodiments of the proposed concept or methods are applicable to othermulti-carrier systems (e.g., an IEEE 802.16m system) withoutrestriction.

FIG. 1 illustrates physical channels and a general method fortransmitting signals on the physical channels in an LTE(-A) system.

Referring to FIG. 1, when a User Equipment (UE) is powered on or entersa new cell, the UE performs initial cell search in step S101. Theinitial cell search involves acquisition of synchronization to anevolved Node B (eNB). Specifically, the UE synchronizes its timing tothe eNB and acquires a cell Identifier (ID) and other information byreceiving a Primary Synchronization Channel (P-SCH) and a SecondarySynchronization Channel (S-SCH) from the eNB. Then the UE may acquireinformation (i.e., a Master Information Block (MIB)) broadcast in thecell by receiving a Physical Broadcast Channel (PBCH) from the eNB.During the initial cell search, the UE may monitor a Downlink (DL)channel state by receiving a DownLink Reference Signal (DL RS).

After the initial cell search, the UE acquires detailed systeminformation (i.e. a System Information Block (SIB)) by receiving aPhysical Downlink Control Channel (PDCCH) and receiving a PhysicalDownlink Shared Channel (PDSCH) based on information included in thePDCCH in step S102.

Then, the UE may perform a random access procedure with the eNB tocomplete the connection to the eNB in step S103 to S106. In the randomaccess procedure, the UE may transmit a preamble on a Physical RandomAccess Channel (PRACH) (S103) and may receive a response message to thepreamble on a PDCCH and a PDSCH associated with the PDCCH (S104). In thecase of contention-based random access, the UE additionally performs acontention resolution procedure including transmission of a PhysicalUplink Shared Channel (PUSCH) (S105) and reception of a PDCCH and itsassociated PDSCH (S106).

After the above procedure, the UE may receive a PDCCH/PDSCH (S107) andtransmit a PUSCH/PUCCH (S108) in a general UL/DL signal transmissionprocedure.

FIG. 2 illustrates a radio frame structure in the LTE(-A) system. The3GPP LTE standards support a type 1 radio frame structure applicable toFrequency Division Duplex (FDD) and a type 2 radio frame structureapplicable to Time Division Duplex (TDD).

FIG. 2(a) is a diagram illustrating the structure of the type 1 radioframe. An FDD radio frame includes only DL subframes or only ULsubframes. The radio frame includes 10 subframes, each subframeincluding two slots in the time domain. One subframe may be 1 ms longand one slot may be 0.5 ms long. One slot includes a plurality of (DL)OFDM symbols or a plurality of (UL) SC-FDMA symbols in the time domain.Unless mentioned otherwise, an OFDM symbol or an SC-FDMA symbol may besimply referred to as a symbol (sym), herein.

FIG. 2(b) illustrates the structure of the type 2 radio frame. A TDDradio frame includes two half frames, each half frame including four(five) general subframes and one (zero) special subframe. The generalsubframes are used for UL or DL according to a UL-DL configuration andthe special subframe includes a Downlink Pilot Time Slot (DwPTS), aGuard Period (GP), and an Uplink Pilot Time Slot (UpPTS). In the specialsubframe, DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE. UpPTS is used for an eNB to perform channelestimation and acquire UL synchronization with a UE. The GP is used tocancel UL interference between a UL and a DL, caused by the multi-pathdelay of a DL signal. A subframe includes two slots.

Table 1 lists exemplary subframe configurations for a radio frameaccording to UL-DL configurations.

TABLE 1 Uplink-downlink Downlink-to-Uplink Subframe number configurationSwitch-point periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 ms D S U UU D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6  5ms D S U U U D S U U D

In Table 1, D represents a DL subframe, U represents a UL subframe, andS represents a special subframe.

FIG. 3 illustrates a resource grid for the duration of one slot. A slotincludes a plurality of symbols (e.g., OFDM symbols or SC-FDMA symbols),for example, 6 or 7 symbols in the time domain by a plurality ofResource Blocks (RBs) in the frequency domain. Each RB includes 12subcarriers. Each element of a resource grid is called a ResourceElement (RE). The RE is a minimum resource unit for signal transmissionand one modulation symbol is mapped to an RE.

FIG. 4 illustrates a structure of a DL subframe. Up to 3 (or 4) OFDMsymbols at the start of the first slot of a DL subframe are used as acontrol region to which a control channel is allocated and the remainingOFDM symbols of the DL subframe are used as a data region to which ashared channel (e.g., a PDSCH) is allocated. DL control channels includea Physical Control Format Indicator Channel (PCFICH), a PDCCH, aPhysical Hybrid automatic repeat request (ARQ) Indicator Channel(PHICH), etc.

The PCFICH is located in the first OFDM symbol of a subframe, carryinginformation about the number of OFDM symbols used for transmission ofcontrol channels in the subframe. The PHICH occupies 4 RE Groups (REGs)distributed equally in the control region based on a cell Identifier(ID). The PCFICH indicates a value ranging 1 to 3 (or 2 to 4) and ismodulated in Quadrature Phase Shift Keying (QPSK). The PHICH delivers anHARQ ACKnowledgment/Negative ACKnowledgment (ACK/NACK) signal as aresponse to a UL transmission. The PHICH is allocated to the remainingREGs of one or more OFDM symbols corresponding to a PHICH duration,except for REGs carrying Cell-specific Reference Signals (CRSs) and thePCFICH (the first OFDM symbol). The PHICH is allocated to 3 REGsdistributed as much as possible in the frequency domain.

The PDCCH delivers information about resource allocation and a transportformat for a Downlink Shared Channel (DL-SCH), information aboutresource allocation and a transport format for an Uplink Shared Channel(UL-SCH), paging information of a Paging Channel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a random access responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, a Transmit Power Control (TPC)command, Voice Over Internet Protocol (VoIP) activation indicationinformation, etc. A plurality of PDCCHs may be transmitted in thecontrol region. A UE may monitor a plurality of PDCCHs. A PDCCH istransmitted in an aggregate of one or more consecutive Control ChannelElements (CCEs). A CCE is a logical allocation unit used to provide aPDCCH at a coding rate based on the state of a radio channel. A CCEincludes a plurality of REGs. The format of a PDCCH and the number ofavailable bits for the PDCCH are determined according to the number ofCCEs.

[Table 2] lists the number of CCEs, the number of REGs, and the numberof PDCCH bits for each PDCCH format.

TABLE 2 PDCCH Number of CCEs Number Number of format (n) of REGs PDCCHbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

The CCEs may be numbered consecutively and a PDCCH having a format withn CCEs may start only at a CCE with an index being a multiple of n. Thenumber of CCEs used for transmission of a specific PDCCH is determinedaccording to a channel condition by an eNB. For example, if the PDCCH isfor a UE having a good DL channel (e.g., a UE near to the eNB), one CCEmay be sufficient for the PDCCH. On the other hand, if the PDCCH is fora UE having a poor channel (e.g., a UE near to a cell edge), 8 CCEs maybe used for the PDCCH in order to achieve sufficient robustness. Inaddition, the power level of the PDCCH may be controlled according tothe channel condition.

Control information transmitted on a PDCCH is called Downlink ControlInformation (DCI). Various DCI formats are defined according to theusages of the DCI. Specifically, DCI formats 0 and 4 (a UL grant) aredefined for UL scheduling and DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B,and 2C (a DL grant) are defined for DL scheduling. Depending on itsusage, a DCI format selectively includes information such as a hoppingflag, an RB assignment, a Modulation Coding Scheme (MCS), a RedundancyVersion (RV), a New Data Indicator (NDI), a TPC, a cyclic shift, aDeModulation Reference Signal (DM-RS), a Channel Quality Information(CQI) re quest, an HARQ process number, a Transmitted Precoding MatrixIndicator (TPMI), Precoding Matrix Indicator (PMI) confirmation, etc.

An eNB determines a PDCCH format according to control information to betransmitted to a UE and adds a Cyclic Redundancy Check (CRC) to thecontrol information, for error detection. The CRC is masked by an ID(e.g., a Radio Network Temporary Identifier (RNTI) according to theowner or usage of a PDCCH. In other words, the PDCCH is CRC-scrambledwith the ID (e.g., the RNTI).

[Table 3] lists exemplary IDs by which a PDCCH is masked.

TABLE 3 Type Identifier Description UE-specific C-RNTI, used for aunique UE identification TC-RNTI, SPS C-RNTI Common P-RNTI used forpaging message SI-RNTI used for system information RA-RNTI used forrandom access response

If a C-RNTI, a Temporary C-RNTI (TC-RNTI), and a Semi-PersistentScheduling C-RNTI (SPS C-RNTI) are used, the PDCCH delivers UE-specificcontrol information for a specific UE. If other RNTIs are used, thePDCCH delivers common control information for all UEs in a cell.

The LTE(-A) standard defines the CCE positions of a limited set(equivalent to a limited CCE set or a limited PDCCH candidate set) inwhich a PDCCH may be located, for each UE. The CCE positions of alimited set that a UE should monitor to detect a PDCCH directed to theUE may be referred to as a Search Space (SS). Monitoring includesdecoding each PDCCH candidate (blind decoding). A UE-specific SearchSpace (USS) and a Common Search Space (CSS) are defined. A USS isconfigured on a UE basis and a CSS is configured commonly for UEs. TheUSS and the CSS may be overlapped. The starting position of the USS hopsbetween subframes UE-specifically. An SS may have a different sizeaccording to a PDCCH format.

[Table 4] lists CSS sizes and USS sizes.

TABLE 4 Number of Number of Number PDCCH PDCCH PDCCH of CCEs candidatescandidates format (n) in CSS in USS 0 1 — 6 1 2 — 6 2 4 4 2 3 8 2 2

To place computation load under control according to the total number ofBlind Decodings (BDs), a UE is not required to detect all defined DCIformats at the same time. In general, the UE always detects formats 0and 1A in a USS. Formats 0 and 1A have the same size and aredistinguished from each other by a flag in a message. The UE may berequired to receive an additional format (e.g., format 1, 1B, or 2according to a PDSCH Transmission Mode (TM) configured by an eNB). TheUE detects formats 1A and 1C in a CSS. The UE may further be configuredto detect format 3 or 3A. Formats 3 and 3A have the same size as formats0 and 1A and may be identified by scrambling a CRC with different IDs(or a common ID), instead of UE-specific IDs.

PDSCH transmission schemes according to TMs and information content ofDCI formats are given as follows.

TMs

-   -   TM 1: transmission from a single eNB antenna port    -   TM 2: transmit diversity    -   TM 3: open-loop spatial multiplexing    -   TM 4: closed-loop spatial multiplexing    -   TM 5: Multi-User Multiple Input Multiple Output (MU-MIMO)    -   TM 6: closed-loop rank-1 precoding    -   TM 7: single-antenna port (port 5) transmission    -   TM 8: double-layer transmission (port 7 and port 8) or        single-antenna port (port 7 or port 8) transmission    -   TMs 9 and 10: up to 8-layer transmission (port 7 to port 14) or        single-antenna port (port 7 or port 8) transmission

DCI Formats

-   -   format 0: resource grant for PUSCH transmission    -   format 1: resource allocation for single-codeword PDSCH        transmission (TMs 1, 2 and 7)    -   format 1A: compact signaling of resource allocation for        single-codeword PDSCH (all modes)    -   format 1B: compact resource allocation for PDSCH (mode 6) using        rank-1 closed-loop precoding    -   format 1C: very compact resource allocation for PDSCH (e.g.,        paging/broadcast system information)    -   format 1D: compact resource allocation for PDSCH using MU-MIMO        (mode 5)    -   format 2: resource allocation for PDSCH of closed-loop MIMO        operation (mode 4)    -   format 2A: resource allocation for PDSCH of open-loop MIMO        operation (mode 3)    -   format 3/3A: power control command having 2-bit/1-bit power        control value for PUCCH and PUSCH    -   format 4: resource grant for PUSCH transmission in a cell set to        multi-antenna port transmission mode

DCI formats may be classified into a TM-dedicated format and a TM-commonformat. The TM-dedicated format is a DCI format configured for acorresponding TM only, and the TM-common format is a DCI formatconfigured commonly for all TMs. For example, DCI format 2B may be aTM-dedicated DCI format for TM 8, DCI format 2C may be a TM-dedicatedDCI format for TM 9, and DCI format 2D may be a TM-dedicated DCI formatfor TM 10. DCI format 1A may be a TM-common DCI format.

FIG. 5 illustrates an example of allocating Enhanced PDCCHs (E-PDCCHs)to a subframe. A legacy LTE system has limitations such as transmissionof a PDCCH in limited OFDM symbols. Accordingly, LTE-A has introducedthe E-PDCCH for more flexible scheduling.

Referring to FIG. 5, a PDCCH conforming legacy LTE(-A) (referred to as alegacy PDCCH or L-PDCCH) may be allocated to a control region (refer toFIG. 4). An L-PDCCH region means a region to which an L-PDCCH may beallocated. The L-PDCCH region may refer to a control region, a controlchannel resource region (i.e., CCE resources) to which a PDCCH may beactually allocated, or a PDCCH SS depending on the context. A PDCCH maybe additionally allocated to a data region (refer to FIG. 4). The PDCCHallocated to the data region is referred to as an E-PDCCH. Asillustrated in FIG. 5, a scheduling constraint imposed by the limitedcontrol channel resources of the L-PDCCH region may be relieved byadditionally securing control channel resources through the E-PDCCH. AnE-PDCCH and a PDSCH are multiplexed in Frequency Division Multiplexing(FDM) in the data region.

Specifically, the E-PDCCH may be detected/demodulated based on DM-RS.The E-PDCCH is transmitted in a Physical Resource Block (PRB) pair alongthe time axis. If E-PDCCH-based scheduling is configured, a subframe inwhich an E-PDCCH will be transmitted/detected may be indicated. TheE-PDCCH may be configured only in a USS. A UE may attempt to detect DCIonly in an L-PDCCH CSS and an E-PDCCH USS in a subframe allowed to carryan E-PDCCH (hereinafter, an E-PDCCH subframe) and in an L-PDCCH CSS andan L-PDCCH USS in a subframe not allowed to carry an E-PDCCH(hereinafter, a non-E-PDCCH subframe).

Like the L-PDCCH, the E-PDCCH delivers DCI. For example, the E-PDCCH maydeliver DL scheduling information and UL scheduling information. AnE-PDCCH/PDSCH operation and an E-PDCCH/PUSCH operation are performed inthe same manner as/a similar manner to steps S107 and S108 of FIG. 1.That is, a UE may receive an E-PDCCH and receive data/controlinformation on a PDSCH corresponding to the E-PDCCH. In addition, the UEmay receive an E-PDCCH and transmit data/control information on a PUSCHcorresponding to the E-PDCCH. In the legacy LTE system, a PDCCHcandidate region (a PDCCH SS) is reserved in a control region and aPDCCH for a specific UE is transmitted in a part of the PDCCH SS.Therefore, a UE may detect its PDCCH in the PDCCH SS by blind decoding.Similarly, an E-PDCCH may also be transmitted in all or a part ofreserved resources.

FIG. 6 illustrates a structure of a UL subframe in the LTE system.

Referring to FIG. 6, a UL subframe includes a plurality of slots (e.g. 2slots). Each slot may include a different number of SC-FDMA symbolsaccording to a Cyclic Prefix (CP) length. The UL subframe is dividedinto a control region and a data region in the frequency domain. A PUSCHcarrying a data signal such as voice or the like is transmitted in thedata region, and a PUCCH carrying Uplink Control Information (UCI) istransmitted in the control region. The PUCCH includes an RB pair locatedat both ends of the data region along the frequency axis and hops over aslot boundary.

The PUCCH may carry the following control information.

-   -   Scheduling Request (SR): information used to request UL-SCH        resources. The SR is transmitted in On-Off Keying (OOK).    -   HARQ response: a response signal to a DL data block (e.g., a        Transport Block (TB)) or a CodeWord (CW) on a PDSCH. The HARQ        response indicates whether the DL data block has been received        successfully. A 1-bit ACK/NACK is transmitted as a response to a        single DL codeword and a 2-bit ACK/NACK is transmitted as a        response to two DL codewords. An HARQ ACK/NACK and an HARQ-ACK        may be interchangeably used in the same meaning of an HARQ        response.    -   Channel Quality Indicator (CSI): feedback information for a DL        channel. MIMO-related feedback information includes an RI and a        PMI. The CQI occupies 20 bits per subframe.

The amount of UCI that a UE may transmit in a subframe depends on thenumber of SC-FDMA symbols available for transmission of the UCI. TheSC-FDMA symbols available for transmission of the UCI are the remainingSC-FDMA symbols except SC-FDMA symbols configured for transmitting RSsin the subframe. The last SC-FDMA symbol of a subframe configured tocarry an SRS is additionally excluded from the SC-FDMA symbols availablefor transmission of the UCI. An RS is used for coherent detection of aPUCCH. A PUCCH supports 7 formats according to information carried onthe PUCCH.

Table 5 illustrates a mapping relationship between PUCCH formats and UCIin the LTE system.

TABLE 5 PUCCH format Uplink Control Information (UCI) format 1SR(Scheduling Request) (non-modulated waveform) format 1a 1-bit HARQACK/NACK (SR present/absent) format 1b 2-bit HARQ ACK/NACK (SRpresent/absent) format 2 CQI (20 coded bits) format 2 CQI and 1- or2-bit HARQ ACK/NACK (20 bits) (only in case of extended CP) format 2aCQI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) format 2b CQI and 2-bitHARQ ACK/NACK (20 + 2 coded bits)

FIG. 7 illustrates an example of mapping PUCCH formats to a PUCCHregion.

Referring to FIG. 7, PUCCH formats are mapped to RBs in the order ofPUCCH format 2/2a/2b (CQI) (e.g. PUCCH region m=0, 1), PUCCH format2/2a/2b (CQI) or PUCCH format 1/1a/1b (SR/HARQ ACK/NACK) (e.g. PUCCHregion m=2 if present), and PUCCH format 1/1a/1b (SR/HARQ ACK/NACK)(e.g. PUCCH region m=3, 4, 5), inward starting from a band edge, andtransmitted. The number of PUCCH RBs, N_(RB) ⁽²⁾ available for PUCCHformat 2/2a/2b (CQI) is indicated to a UE in a cell by broadcastsignaling.

FIG. 7 illustrates a random access procedure. The random accessprocedure is used to transmit UL short data. For example, uponoccurrence of initial access in Radio Resource Control (RRC)_IDLE mode,initial access after Radio Link Failure (RLF), or handover requiringrandom access, or upon generation of UL/DL data requiring random accessin RRC_CONNECTED mode, the random access procedure is performed. Therandom access procedure is performed in a contention-based manner or anon-contention-based manner.

Referring to FIG. 7, a UE receives random access information from an eNBby system information and stores the received random access information.Subsequently, when random access is needed, the UE transmits a randomaccess preamble (message 1 or Msg1) to the eNB on a PRACH (S810). Uponreceipt of the random access preamble from the UE, the eNB transmits arandom access response message (message 2 or Msg2) to the UE (S820).Specifically, DL scheduling information for the random access responsemessage is CRC-masked by a Random Access-RNTI (RA-RNTI) and transmittedon a PDCCH. Upon receipt of the DL scheduling signal masked by theRA-RNTI, the UE may receive the random access response message on aPDSCH. Then, the UE determines whether a Random Access Response (RAR)directed to the UE is included in the random access response message.The RAR includes a Timing Advance (TA), UL resource allocationinformation (a UL grant), a temporary UE ID, etc. The UE transmits aUL-SCH message (message 3 or Msg3) to the eNB according to the UL grant(S830). After receiving the UL-SCH message, the eNB transmits acontention resolution message (message 4 or Msg4) to the UE (S840).

Meanwhile, the UE may be stipulated to simultaneously receive aplurality of data for a specific data combination. Table 6 and Table 7show combinations of physical/transport channels a single UE cansimultaneously receive in the same subframe. Particularly, Table 6 showsdownlink reception types and Table 7 shows combinations of downlinkreception types.

TABLE 6 Associated “Reception Physical Monitored Transport Type”Channel(s) RNTI Channel A PBCH N/A BCH B PDCCH + PDSCH SI-RNTI DL-SCH CPDCCH + PDSCH P-RNTI PCH D PDCCH + PDSCH RA-RNTI (Note 3) DL-SCHTemporary C-RNTI DL-SCH (Note 3) (Note 4) (PDCCH/EPDCCH) + C-RNTI andDL-SCH PDSCH Semi-Persistent Scheduling C-RNTI  D1 (PDCCH/EPDCCH) +C-RNTI DL-SCH PDSCH (Note 9) E PDCCH/EPDCCH C-RNTI N/A (Note 1) F PDCCHTemporary C-RNTI UL-SCH (Note 5) PDCCH/EPDCCH C-RNTI and UL-SCHSemi-Persistent Scheduling C-RNTI  F1 PDCCH/EPDCCH C-RNTI UL-SCH (Note9) G PDCCH TPC-PUCCH-RNTI N/A H PDCCH TPC-PUSCH-RNTI N/A I PDCCH/EPDCCHSemi-Persistent N/A Scheduling C-RNTI (Note 6) J PDCCH/EPDCCHSemi-Persistent N/A Scheduling C-RNTI (Note 7) K PDCCH M-RNTI (Note 8)N/A L PMCH N/A (Note 8) MCH Note 1: PDCCH or EPDCCH is used to conveyPDCCH order for Random Access. Note 2: Void. Note 3: RA-RNTI andTemporary C-RNTI are mutually exclusive and only applicable duringRandom Access procedure. Note 4: Temporary C-RNTI is only applicablewhen no valid C-RNTI is available. Note 5: Temporary C-RNTI is onlyapplicable during contention-based Random Access procedure. Note 6:Semi-Persistent Scheduling C-RNTI is used for DL Semi-PersistentScheduling release. Note 7: Semi-Persistent Scheduling C-RNTI is usedfor UL Semi-Persistent Scheduling release. Note 8: In MBSFN

s only Note 9: DL-SCH reception corresponding to D1, and UL-SCHtransmission corresponding to F1, are only applicable to SCells.

TABLE 7 Combination Mandatory/Optional Comment 1 × A + 1 × 13 + 1 × CMandatory RRC_IDLE 1 × K + 1 × L Mandatory for MBMS UEs RRC_IDLE 1 × A +1 × B + 1 × (D or (1 − m) × E or G or I) + (p − 1 − m) × Mandatory.(NOTE 3) RRC_CONNECTED D1 + m × E + 1 × (F or H or J) + (q − 1) × F1 1 ×A + 1 × B + 1 × (D or (1 − m) × E or G or I) + 1 × (F or H or Mandatoryfor UEs supporting RRC_CONNECTED J) + 1 × F + (p − 1 − m) × D1 + m × E +2 × (q − 1) × F1 FS2. (NOTE 3) (NOTE 4) (NOTE 1) ((1 × ((1 − m) × E or Gor I) + t × L) or 1 × D) + 1 × (F or H or Mandatory for MBMS UEs.RRC_CONNECTED J) + r × K + (p − 1 − m) × D1 + m × E + (q − 1) × F1 + (r− t) × (NOTE 3) (NOTE 4) (NOTE 2) L + (r − t + 1) × (A + B) ((1 × ((1 −m) × E or G or I) + t × L) or 1 × D) + 1 × (F or H or Mandatory for MBMSUEs RRC_CONNECTED J) + 1 × F + r × K + (p − 1 − m) × D1 + m × E + 2 × (q− 1) × supporting FS2. (NOTE 3) (NOTE 1) (NOTE 2) F1 + (r − t) × L + (r− t + 1) × (A + B) 1 × A + 1 × B + 1 × C + 1 × (D or (1 − m) × E or G orI) + (p − Mandatory for ETWS and RRC_CONNECTED 1 − m) × D1 + m × E + 1 ×(F or H or J) + (q − 1) × F1 CMAS UEs Optional for all other UEs. (NOTE3) 1 × A + 1 × B + 1 × C + 1 × (D or (1 − m) × E or G or I) + 1 ×Mandatory for ETWS and RRC_CONNECTED (F or H or J) + 1 × F + (p − 1 − m)× D1 + m × E + 2 × (q − CMAS UEs supporting FS2 (NOTE 1) 1) × F1Optional for all other UEs. (NOTE 3) NOTE 1: For TDD UL/DL configuration0, two PDCCHs or EPDCCHs can be received in the same subframe for UL-SCHin two different uplink subframes. NOTE 2: The combination is therequirement when MBMS reception is on PCell and/or any other cell. r isthe number of DL CCs on which the UE supports MBMS reception accordingto the MBMSInterestIndication. t = 1 if there is PMCH reception in thePCell, otherwise t = 0. PDSCH and PMCH are mutually exclusive in thesame subframe on a cell. NOTE: p is the number of DL CCs supported bythe UE. q is the number of UL CCs supported by the UE. q = p = 1 impliesnon-CA capable UE. m = 0 or 1 for UE supporting multiple TAGs, otherwisem = 0. NOTE: The UE is only required to receive one PDSCH, pertaining toD or D1, per DL CC. NOTE 3: Combination involving EPDCCH is optional andrequired only for UE supporting EPDCCH. NOTE 4: It is not required tosimultaneously receive EPDCCH and PMCH on the same cell.

Embodiment A Signal Transmission/Processing for a Low-Price UserEquipment

A low cost/low capability UE centering on data communications of meterinspection, water level measurement, monitoring camera utilization,vending machine stock report and the like is currently considered by anext-generation system of LTE-A. Such a UE is called LC (Low Cost) UE(or, LC type, LC type UE) (e.g., MTC (Machine Type Communication) UE)for clarity. The LC UE can be defined as a UE of a specific categorybased on a UE capability category. In case of the LC UE, the amount ofdata transmitted is small and uplink/downlink datatransmission/reception does not frequently occur, and thus it isefficient to reduce the unit cost of the UE and reduce batteryconsumption according to the low data transmission rate. Furthermore,the LC UE has the feature that mobility is low and the channelenvironment rarely changes. In consideration of a poor situation that anLC UE is installed in a coverage-limited place such as a building, afactory, a basement or the like in the future, various coverageenhancement schemes for each channel/signal are under discussion. Forexample, a method of repeatedly transmitting a channel/signal is underdiscussion in order to enhance the coverage.

Meanwhile, the reduction of the number of receiving antennas, thereduction of the maximum TB size, the reduction of the receiving buffersize and the like are under consideration as a technology for a lowprice/low specification LC UE. In case of the reduction of the maximumTB size, in order to efficiently reduce the decoding complexity/latencyfor the DL received data (e.g., PDSCH) having a great influence upon theunit cost/costs of the LC UE, the maximum TB size (e.g., the bit number)of the UE-common data (hereinafter, common data) and the maximum TB sizeof the UE-specific data (hereinafter, unicast data) can be differentlydefined. This is because a mainly applicable appropriate message sizeand/or a required coding rate vary depending on the data type (i.e.,common data and unicast data).

The common data may include data associated with SI-RNTI, P-RNTI andRA-RNTI (i.e., SIB, a paging message and RAR). The unicast data mayinclude data associated with C-RATI, SPS C-RNTI and TC-RNTI (i.e., dataabout an individual UE). Therefore, a scrambling based on SI-RNTI,P-RNTI or RA-RATI may apply to a PDCHH scheduling a PDSCH (common data)and a scrambling based on C-RNTI, SPS C-RNTI or TC-RNTI may apply to aPDCCH for scheduling a PDSCH (unicast data).

Meanwhile, a plurality of data can be simultaneouslyscheduled/transmitted through one subframe and an LC UE can bestipulated to simultaneously receive a plurality of data for a specificdata combination. According to a related art, for example (see Table 6and Table 7), an LC UE can be stipulated to simultaneously receive anSIB and a paging which are simultaneously scheduled/transmitted throughone subframe in RRC idle mode. Further, in RRC-connected mode, an LC UEcan be stipulated to simultaneously receive an SIB and an RAR or an SIBand unicast data which are simultaneously scheduled/transmitted throughone subframe. Particularly, when the LC UE is restricted to support asingle DL CC, a specific data combination simultaneously receivable bythe LC UE may correspond to a case that p=q=1 and m=0 in Table 7.

When the maximum TB sizes corresponding to common data and unicast datafor the LC UE are differently defined, (particularly, in RRC-connectedmode) a simultaneously receivable maximum TB size combination (for eachdata type) may need to be defined. In this case, when the maximum TBsize corresponding to a specific data type is differently defineddepending on the data transmission phase, an effective received signalprocessing operation of the UE may be necessary. For example, if themaximum TB size corresponding to a specific data type is differentlystipulated depending on a case of solely receiving the correspondingdata type or a case of simultaneously receiving the corresponding datatype together with another data type, an effective received signalprocessing operation of the UE may be necessary.

A data receiving method/operation of an LC UE is proposed below. Thepresent invention may be limited to a case that the LC UE is inRRC-connected mode. Unless indicated otherwise, the UE indicates an LCUE. For clarity, the following terms are defined.

-   -   Common data: Common data indicates data transmitted to a        plurality of user equipments. Common data includes        SIB/paging/RAR. And, the SIB/paging/RAR is associated with        SI-RNTI-/P-RNTI/RA-RNTI. Particularly, common data is        transmitted through a PDSCH and an SI-RNTI/P-RNTI/RA-RNTI based        scrambling may apply to a PDCCH for scheduling a PDSCH (common        data). An RNTI-based scrambling includes a scrambling (e.g.,        XOR) of CRC of PDCCH with RNTI.    -   Unicast data: Unicast data indicates data transmitted to a        single user equipment. Unicast data is associated with        C-RNTI/SPS C-RNTI/TC-RNTI. Particularly, unicast data may be        transmitted through a PDSCH and a C-RNTI/SPS C-RNTI/TC-RNTI        based scrambling may apply to a PDCCH for scheduling the PDSCH        (unicast data). An RNTI-based scrambling includes a scrambling        (e.g., XOR) of CRC of PDCCH with RNTI.    -   Dedicated data: RAR, unicast data    -   Tc: The maximum TB size of common data when the common data is        solely received    -   Tu: The maximum TB size of unicast data when unicast data is        solely received    -   Ts: The maximum TB size of common data when common data (e.g.,        an SIB) and dedicated data are simultaneously received    -   Td: The maximum TB size of dedicated data when common data        (e.g., an SIB) and dedicated data are simultaneously received

It is assumed that the relation of maximum TB sizes is Tc=Ts>Tu=Td. Incase of specific data (e.g., RAR), the maximum TB size Tc at theindividual reception and the maximum TB size Td at the simultaneousreception can be differently set (i.e., Tc>Td). In this case, themaximum Tb size indicates the maximum TB size that can be processed bythe UE. The unit of the TB size is a bit.

Hence, the present invention proposes a method/operation ofsimultaneously receiving a plurality of data in the case that specificdata (e.g., RAR) (hereinafter, RAR) is included in common data anddedicated data in common. Particularly, the present invention proposes amethod/operation of receiving data in a situation that the actual TBsize of RAR scheduled/transmitted simultaneously with common data (e.g.,an SIB) through one subframe exceeds the maximum TB size Tdcorresponding to the simultaneous reception (while not exceeding themaximum TB size Tc corresponding to individual reception). For clarity,TB sizes applied to actual scheduling/transmission of common data (e.g.,SIB) (hereinafter, SIB) and RAR are defined as T_sib and T_rar,respectively.

Case 1) Case of Td<T_sib≦Ts (=Tc), Td<T_rar (≦Tc=Ts)

In a current situation, SIB is equal to or smaller than the maximum TBsize and exceeds the maximum TB size corresponding to RAR and the RARexceeds the corresponding maximum size. In this case, the UE may selectonly one data from SIB and RAR and then receives the selected one data(option 1-1), or may omit reception of both SIB and RAR (option 1-2). Incase of option 1-1, the UE may i) always select RAR, ii) always selectSIB, or iii) select SIB when RAR is received as a part of an RACHprocess based on contention (or not accompanied by PDCCH order) andselect RAR when RAR is received as a part of an RACH process based onnon-contention (or accompanied by PDCCH order).

In the present specification, selecting and receiving data includesperforming a received signal processing (e.g., decoding or the like) onselected data only. Further, omitting data reception includes omitting areceived signal processing (e.g., decoding or the like) on PDSCHindicated by PDCCH. The TB size of the PDSCH can be obtained throughscheduling information of the corresponding PDCCH.

Meanwhile, the present method can apply to a UE (reception) operation ina situation that each of SIB and RAR exceeds the maximum TB sizecorresponding to unicast data Tu=Td. Namely, the present method canapply to the UE reception operation in the case that Tu<T_sib≦Ts=Tc,Tu<T_rar≦Tc=Ts. In this case, the UE may selects only one data from SIBand RAR and then receives the selected data only, or may omit receptionof both SIB and RAR. In the former case, the UE may i) always selectRAR, ii) always select SIB, or iii) select SIB when RAR is received as apart of an RACH process based on contention (or not accompanied by PDCCHorder) and select RAR when RAR is received as a part of an RACH processbased on non-contention (or accompanied by PDCCH order). Meanwhile, inother cases (e.g., when only one of SIB and RAR exceeds the maximum TBsize corresponding to unicast data Tu=Td), simultaneous reception may beperformed for both SIB and RAR. Namely, in the case that (i) T_sib≦Tu,Tu<T_rar≦Tc=Ts and (ii) Tu<T_sib≦Ts=Tc, T_rar≦Tu, the UE can performsimultaneous reception for both SIB and RAR.

FIG. 8 illustrates an example of a process for receiving a downlinksignal according to one embodiment of the present invention.

Referring to FIG. 8, a user equipment (UE) can receive a first PDCCHincluding scheduling information on a first common data in a subframe(e.g., subframe n) (S802). Further, the UE can receive a second PDCCHincluding scheduling information on a second common data in the samesubframe (i.e., subframe n). Thereafter, the UE may perform/control aprocess for receiving downlink data in the subframe n based on TB sizeTa of the first common data and TB size Tb of the second common data(S806). If T1<Ta≦T2 and T1<Tb≦T2, a reception (a signal processing) canbe selectively performed on only one of the first common data and thesecond common data. Meanwhile, if Ta≦T1 and T1<Tb≦T2 or T1<Ta≦T2 and TbT1, a reception (a signal processing) can be performed on both of thefirst common data and the second common data. In this case, T1 indicatesthe maximum TB size at the time of solely receiving unicast data. T2indicates the maximum TB size at the time of solely receiving commondata.

In this case, the first common data may include SIB and the secondcommon data may include RAR. In this case, when T1<Ta≦T2 and T1<Tb≦T2, areceived signal processing may be performed on only SIB among SIB andRAR or the received signal processing may be performed on only RAR.Further, if T1<Ta≦T2 and T1<Tb≦T2, when RAR is transmitted as a part ofa contention-based RACH (Random Access Channel) process, a receivedsignal processing may be performed on only SIB among SIB and RAR. Or,when RAR is transmitted as a part of a non-contention-based RACHprocess, the received signal processing may be performed on only RARamong SIB and RAR. The received signal processing includes decoding TB.In the case that a reception (a signal processing) is performed on onlyone of a plurality of data, a reception of other data may be omitted. Tothis end, when the UE detects a PDCCH including scheduling informationon the reception-omitted data, the UE can omit a received signalprocessing (e.g., decoding) for the PDSCH indicated by the correspondingPDCCH.

Case 2) Case of T_sib≦Td, Td<T_rar (≦Tc=Ts)

In a current state, SIB is equal to or smaller than the correspondingmaximum TB size and is equal to or smaller than the maximum TB sizecorresponding to RAR. In a current station, the RAR exceeds thecorresponding maximum size. In this case, the UE may simultaneouslyreceive both of the SIB and the RAR (option 2-1) or may omit receptionof both of the SIB and the RAR (option 2-2). In case of option 2-1, theUE is already equipped with all decoders corresponding to the two kindsof the maximum TB sizes (i.e., Ts and Td), and thus it may be possibleto simultaneously receive both of the SIB and the RAR, each of which hasan actual TB size like the present example.

Case 3) Case of T_sib>Ts (=Tc), Td<T_rar (≦Tc=Ts)

In a current situation, each of SIB and RAR exceeds a correspondingmaximum TB size. In this case, the UE can receive only RAR (option 3-1)or omit reception of both of the SIB and the RAR (option 3-2). In caseof option 3-1, the UE is already equipped with a decoder correspondingto the maximum TB size Ts, and thus it may be possible to receive RARhaving an actual TB size equal to or smaller than Ts.

FIG. 9 illustrates a BS and a UE, which are applicable to embodiments ofthe present invention.

Referring to FIG. 9, the wireless communication system includes a BS 110and a UE 120. The BS 110 includes a processor 112, a memory 114 and aradio frequency (RF) unit 116. The processor 112 may be configured toimplement the procedures and/or methods proposed by the presentinvention. The memory 114 is connected to the processor 112 and storesinformation related to operations of the processor 112. The RF unit 116is connected to the processor 112 and transmits and/or receives an RFsignal. The UE 120 includes a processor 122, a memory 124 and an RF unit126. The processor 122 may be configured to implement the proceduresand/or methods proposed by the present invention. The memory 124 isconnected to the processor 122 and stores information related tooperations of the processor 122. The RF unit 126 is connected to theprocessor 122 and transmits and/or receives an RF signal. The BS 110and/or the UE 120 may include a single antenna or multiple antennas.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The termSUE′ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a method and apparatus forperforming communication in a case that an MTC is supported in awireless communication system.

1. A method of receiving a downlink signal by a user equipment in awireless communication system, the method comprising: receiving a firstPDCCH (Physical Downlink Control Channel) including a schedulinginformation on a first common data in a subframe; receiving a secondPDCCH including a scheduling information on a second common data in thesubframe; and controlling a process for receiving a downlink data in thesubframe based on TB (Transport Block) size Ta of the first common dataand TB size Tb of the second common data, wherein if T1<Ta≦T2 andT1<Tb≦T2, a received signal processing is performed on either the firstcommon data or the second common data, wherein if Ta≦T1 and T1<Tb≦T2 orT1<Ta≦T2 and Tb≦T1, the received signal processing is performed on boththe first common data and the second common data, wherein the T1indicates a maximum TB size in case of receiving a unicast data solely,and wherein the T2 indicates a maximum TB size in case of receiving acommon data solely.
 2. The method of claim 1, wherein the first commondata comprises an SIB (System Information Block), and the second commondata comprises an RAR (Random Access Response).
 3. The method of claim2, wherein if T1<Ta≦T2 and T1<Tb≦T2, the received signal processing isperformed on only the SIB among the SIB and the RAR.
 4. The method ofclaim 2, wherein if T1<Ta≦T2 and T1<Tb≦T2, the received signalprocessing is performed on only the RAR among the SIB and the RAR. 5.The method of claim 2, wherein if T1<Ta≦T2 and T1<Tb≦T2 and if the RARis transmitted as a part of a contention-based RACH (Random AccessChannel), the received signal processing is performed on only the SIBamong the SIB and the RAR.
 6. The method of claim 2, wherein if T1<Ta≦T2and T1<Tb≦T2 and if the RAR is transmitted as a part of anon-contention-based RACH process, the received signal processing isperformed on only the RAR among the SIB and the RAR.
 7. A user equipmentused for a wireless communication system, comprising: an RF (RadioFrequency) unit; and a processor, wherein the processor is configuredto: receive a first PDCCH (Physical Downlink Control Channel) includinga scheduling information on a first common data in a subframe; receive asecond PDCCH including a scheduling information on a second common datain the subframe; and control a process for receiving a downlink data inthe subframe based on TB (Transport Block) size Ta of the first commondata and TB size Tb of the second common data, wherein if T1<Ta≦T2 andT1<Tb≦T2, a received signal processing is performed on either the firstcommon data or the second common data, wherein if Ta≦T1 and T1<Tb≦T2 orT1<Ta≦T2 and Tb≦T1, the received signal processing is performed on boththe first common data and the second common data, wherein the T1indicates a maximum TB size in case of receiving a unicast data solelyand wherein the T2 indicates a maximum TB size in case of receiving acommon data solely.
 8. The user equipment of claim 7, wherein the firstcommon data comprises an SIB (System Information Block), and the secondcommon data comprises an RAR (Random Access Response).
 9. The userequipment of claim 8, wherein if T1<Ta≦T2 and T1<Tb≦T2, the receivedsignal processing is performed on only the SIB among the SIB and theRAR.
 10. The user equipment of claim 8, wherein if T1<Ta≦T2 andT1<Tb≦T2, the received signal processing is performed on only the RARamong the SIB and the RAR.
 11. The user equipment of claim 8, wherein ifT1<Ta≦T2 and T1<Tb≦T2 and if the RAR is transmitted as a part of acontention-based RACH (Random Access Channel), the received signalprocessing is performed on only the SIB among the SIB and the RAR. 12.The user equipment of claim 8, wherein if T1<Ta≦T2 and T1<Tb≦T2 and ifthe RAR is transmitted as a part of a non-contention-based RACH process,the received signal processing is performed on only the RAR among theSIB and the RAR.